Ethernet is rapidly becoming the protocol of choice for consumer, enterprise and carrier networks. It is expected that most networks will evolve such that Ethernet will be the technology used to transport all the multimedia applications including, for example, triple-play, fixed-mobile-convergence (FMC), and IP multimedia sub-systems (IMS). Existing network elements which offer network access using Ethernet technology are not designed to make maximum use of the legacy network links existing at the edge of the carrier networks. The edge of the network is quickly becoming a bottleneck as the new applications are becoming more and more demanding for bandwidth.
Telecommunications carriers are constantly looking for new revenue sources. They need to be able to deploy rapidly a wide ranging variety of services and applications without the need to constantly modify the network infrastructure. Ethernet is a promising technology that is able to support a variety of application requiring different quality of service (QoS) from the network. The technology is now being standardized to offer different types of services which have different combinations of quality objectives, such as loss, delay and bandwidth. Bandwidth objectives are defined in terms committed information rate (CIR) or excess information rate (EIR). The CIR guarantees bandwidth to a connection while the EIR allows it to send at higher bandwidth when available.
Path Association
Using MPLS, bidirectional connections are set up using two uni-directional tunnels. A concept of pseudo-wire has been standardized to pair the two tunnels at both end-points of the tunnels (see FIG. 1). However intermediate nodes are not aware of the pairing and treat the two tunnels independently. Furthermore, the routing mechanism does not attempt to route both connections through the same path. It is therefore impossible for a carrier to use operation administration and maintenance (OAM) packets, in order to create loopbacks within the connection path to troubleshoot a connection without setting up out-of-service explicit paths. There is therefore a need for a mechanism to make a unidirectional path look like a bi-directional path.
This capability existed in ATM and frame relay technologies because they were inherently connection-oriented and both paths of a connection (forward and backward) always went through the same route.
Carriers need the ability to set up flexible Ethernet OAM path in-service and out-of-service anywhere in the network in order to efficiently perform troubleshooting.
E-LINE Protection
In order to provide reliable carrier-grade Ethernet services, the Ethernet technology has to be able to support stringent protection mechanisms for each Ethernet point-to-point (E-LINE) link.
There are two main types of protection required by a carrier, link protection and path protection. There are a number of standard link protection techniques in the marketplace, such as ring protection and bypass links which protect against a node going down. Generally connection oriented protocols such as MPLS use path protection techniques. Most path protection techniques assume a routed network where the routes are dynamically configured and protected based on the resource requirements.
One issue with all these existing protection protocols is that they do not take into account business policies, such as desired level of protection, for determining the protected path.
Another issue with the current way protection paths are set up is that they only trigger when intermediate nodes or links encounter failure. If the end-point outside of the tunnel, receiving the traffic fails, the source continues to send the traffic unaware of the failure, until application-level reaction is triggered, thus wasting precious bandwidth. Such reaction can take up to several minutes.
Zero-Loss Proctection Switching
Some communication applications, such as medical and security applications, require a very reliable service. In these cases, a 50-ms switch over time may be inadequate due to the critical data lost during this time period. For example, a 50-ms switch over in a security monitoring application could be misconstrued as a “man-in-the-middle” attack, causing resources to be wasted resolving the cause of the “glitch.”